If you have market and smith, the market gives +1 action that lets u play the smith and get +four cards. Then if you draw gold that will give you money so you can buy province. This combo is strong because the market ALSO gives money, and lets u buy more money (free!!): but problem is sometimes you dont draw market and smith together

Guess I'll have to be the one to ask: What's your other account name, and why have you decided to start trolling us?

From their post history, the first two only had me like 60% convinced they're trolling, but "i think the best card is harbinger" puts it over the top..

No one would seriously claim that, whereas a troll would

Actually, the first game I played with Harbinger I think also had Mystic, which is a pretty nice synergy, so I overestimated Harbinger for a while until I realized that Mystic was pulling most of the weight in that synergy. I never would have called it the best card though.

Basically, Watchtower gives you a 1 Buy --> x coin conversion option in your buy phase, where x is 2 times the number of Priests you've played this turn. You may want to keep some of the Coppers you buy, though, to fuel the Priests for next turn.